Benzothiazole polyamides



3,260,700 Un1ted States Patent 0 ice My ,66

3260 700 comonorlirers lproilllide a copolyamide of heat resistance approac mg t e omopolymer; thus these materials are BENZOTH A Q POLYAMIDES suitable for the preparation of molded objects markedly Bernard Rudnet and Plump Bmmfield Pmsburgh and resistant to shock and high temperatures.

Paul M. Hergenrother Wampum Pa. assignors to It 15, therefore, an object of the present invention to Koppers Company, Inc., a corporation of Delaware No Drawing. Filed Sept. 19, 1962, Ser. No. 224,824 l-" novel p y C ta ning benzothiazole nu- 8 Claims. (Cl. 260-47) clei, which are characterized by substantially improved thermal, oxidative and hydrolytic stabilit This mvention relates to polymeric lmear condensation- In accordance with the invention we have discovered type polyamides derived from compounds containing 10 a novel homopolymnide of the formula benzothiazole nuclei. In one specific aspect, 1t relates to novel benzothiazole homopolyamides characterized by O "I greater heat stability than any polyamide heretofore ii known. In a further aspect, it relates to heat-stable co- C C polyamides containing benzothiazole nuclei which are L L 1 good fiber formers and which have exceptional dye receptivity.

The common commercial polyamides are those derived wherein x is an integer having a value of 1 to 5 and y is an integer having a value of at least 2, which is made by from caprolactam (the so caued nylon Qwaminoum heat ng at a temperature of 180 -450 C., preferably 220- decanoic acid and the combination of adipic 420 C., 1n the presence of a catalyst if desired, a comacid with hexamethylencdiamine (nylon 66). Although Pound of the formula:

these materials have achieved vast commercial success in O s S the preparation of fibers and molded objects, their thermal, H f 1 -NHR, oxidative and hydrolytic stability afford inherent limita- 1 0' C tions on possible uses.

We have discovered a new class of polyamides containing benzothiazole nuclei which, unexpectedly, have wherein x has the value given aforesaid, R is hydroxy greater thermal, oxidative and hydrolytic stability than halogen, lower alkoxy or phenoxy and R is hydrogen 0;- any polyamide heretofore known. Our new polymers are n acyl, preferably lower alkanoyl. also characterized by increased melting point and soften- 0 We have also discovered new copolyamides of the ing ranges. formula:

iictnm itg xtg xhgf L t A l. l,

None of the polyamides heretofore known contain a whereinR is apredominantly hydrocarbon residue having benzothiazole nucleus, although polymers containing such from 2-16 carbon atoms, more specifically a member a nucleus are described in Morton et al., US. Patent selected from the group consisting of arylene radicals 3,047,543. The polymers of Morton are useful adhesive having from 6 to 16 carbon atoms and alkylene radicals components and must be made from a critical mixture of having from 2 to 12 carbon atoms, 2 is an integer having ill monomeric isomers in order to obtain a proper reaction a value of 1 to 2, x is an integer having a value of 1 to 5 and a polymer of the desired properties. We have not m has a minimum value of 1 and a maximum value sucli experienced this limitation in connection with the preparathat the ratio of m-l/n is no greater than 20 n has a tion of our polyamides. Our polymers also differ from value of 1, and q is an integer having a value of at least 2 those of Morton in that they are crystalline fiber formers The copolyamides of the invention are made by heating at by virtue of hydrogen bonding of the a temperature of 180-450 C., in the presence of a catalyst O H if desired, a benzothiazole compound of the formula: n l

o g f 1 NHR group, which also gives them greater dye receptivity plus R10 9 C ability to be cross-linked, e.g. by condensation with alde- L J hydes.

The polyamides of the invention are useful in various wherein 1 and 2 h e the values given aforesaid with commercial and military applications wherein thermal either (a) an amino carboxy acid of t e formula: stability and shock resistance are particular requirements. R

The homopolyamides, because of their ability to withstand 2 v 1 temperatures up to about 580 C., are suitable materials for rocket nose cones. The use of the copolyamides varies with the structure of the comonomer polymer zed with the monomer containing the benzothrazole unit. The copolyamides derived from the aliphatic-type comonomer are excellent fiber formers and provide nylonetype fibers of improved st'iiness and heat stability. Aromatic-type R1 wherein R, R and R have the values given aforesaid or 0 (b) an equimolar mixture of a diamine of the formula:

and a diacid of the formula:

wherein R, R and R have the values given aforesaid, the quantity of the benzothiazole compound being at least mole percent of the reaction mixture (i.e. m-21, n-l in the copolyamide formula). In the case of the diamine and the diacid, R may represent a different member of the same group in each of the compounds, e.g. R of the diamine may be biphenylene and R of the diacid oxy-bisphenylene. The value of p in the formula of the copolymer is one if an amino-acid is used as a reactant, and two if the comonomer is a mixture of a diamine and diacid or its equivalent.

The new polymers of the invention are readily derived, e.g. from commercially available dehydrothio-p-toluidine (x=1, below) and the equally available mixture of higher condensates (x=2, chiefly, with some x=3, 4 and 5 also present) generally sold as primuline base:

CH3 r s l L N T NHz CzHaOz It has been possible to push the single preparation reaction to give products of higher value of x. It has also been possible, for example, by starting with m-toluidine, to obtain related materials.

To make the monomers useful in the invention the methyl group of the dehydrothiotoluidine or its higher condensation product is oxidized to the corresponding carboxylic acid. This is conveniently accomplished by protecting theamino group by acetylation and subsequently oxidizing the resulting acetyl derivative. The acetamidobenzothiazole carboxylic acid can be used as such in the preparation of the novel homopolyamide, since the acetyl group is removed by heating and converted to the free amine during polymerization. Other means of protecting the amino group can be used, e.g. conversion to a benzene sulfonyl derivative or an azo dye.

Polymerization is accomplished by heating the monomeric material to a temperature between about 180 and than the parent amino-acid. In general, ticularly with aliphatic components, proceed better at lower temperatures, since higher temperatures tend to cause degradation.

formula is 2-4), under mild conditions; for example, heating t-butyl 2-(4'-acetamidophenyl)benzothiazolecarboxylate in a vacuum at 250 C. until approximately from one-half to three-quarters the theoretical weight loss has been realized, then completing the polymerization as a compression molding at, say, 12,000 p.s.i.g. and 350 C. The final product, under these conditions, is a cured, insoluble and infusible rigid body, resistant to ablation as well as thermal degration, having a molecular weight estimated to be at least 300,000 (q is 30-50). We have found our products to be most useful when their molecular Weights range from approximately 10,000 on up. Lower molecular Weight products, such as the carefully synthesized although not really a polymer, are useful as prepolymers in creating strong bonds between surfaces.

Although often most convenient, the dry-melt polymerization procedure described above is not always the best addition product of glutaric anhydride and 2-(3'-aminophenyl)benzothiazole-S-carboxylic acid, converted to its diacid chloride, reacts in organic solution with an aqueous alkaline solution of b1s-(2-aminoethoxy)ethane to give the polymer at the interface. The liquid media used need not be unreactive, but they must not exert a degradative effect on the polymer as it forms. For example, use of a solvent that reacts readily with water (acetic anhydride or polythe formation of the desired product.

If desired, conventional polyamide polymerization catalysts, such as the m-xylenediamine salt of isophthalic acid, metal alkoxides, acids or bases, can be used to shorten the polymerization time. If used, the catalyst is present in an amount of 0.52 percent by Weight of the combined reactants.

or its useful derivatives. As noted hereabove, R in the above formula represents a primarily hydrocarbon residue having from 2-16 carbon atoms, more specifically an arylene radical having from 616 carbon atoms or an alkylene radical having from 2-12 carbon atoms.

Particularly useful aromatic amino-acids are those in which the arylene radical is phenylene, bis-phenylene, oxy-bis-phenylene, thio-bis-phenylene, sulfonyl-bis-phenylene, and bis-naphthylene, including the halo, lower alkoxy or lower alkyl-substituted derivatives of the foregoing. Specific useful aromatic acids thus include p-aminobenzoic acid, anthranilic acid, (3-aminophenylsulfonyl)benzoic acid, 3-aminocarbazole-6-carboxylic acid, 3-aminobipyridyl-(6,6')-3-carboxylic acid, 2-(2) naphthoxy 5- amino-S-naphthoic acid, 2-(3-aminophenyl)-2-(4-carboxyphenyl)propane, and the like.

If R is aliphatic, the useful comonomers thus include the simple amino-acids having from 2-12 carbon atoms including ll-aminoundecanoic acid, S-amino-S-methylheptanoic acid, 2-aminopropionic acid, pyrrolidone, caprolactam, phenylacetylaminovalerate, and the like.

Alternatively, the copolyamides can be made by polymerizing the benzothiazole amino-acid in the presence of equimolar quantities of a diamine of the formula:

H N--R-NH (or its useful derivatives) and a diacid of the formula: HOOC-RCOOH (or its useful derivatives) wherein R has the value given aforesaid. As noted hereabove, if the diamine and diacid are used, the R of each may be a different substituent. Useful diamines which can be mixed with the diacids include 4,4-oxydianiline, benzidine, 3,3'-dialkoxybenzidine, 3,3-dimethylbenzidine, 3,4-sulfonyldianiline, fluorene-3,7-diamine, p-xy-lylenediamine, cyclohexylidenebis-(p-aniline), 3,S-bis-(aminomethyl)pyridine, Z-phenylbenzothiazolylenediamine 5,4, ethylenediamine, propylenediamine, 1,4-diaminobutene-2, menthanediamine, 1,3- dimethylcyclobutyl 1,3 diamine, oxy-bis-(3-aminopropane), and the like. Useful diacids include oxy-bis-(4- 'benzoic) acid, phenylbenzothiazole-4,5-dicarboxylic acid, sulfonyl-bis-nicotinic acid, suberic acid, hexahydroterephthalic acid, phenylthionaphthyldicarboxylic acids, and the like.

The preparation of the copolyamides of the invention can be conducted as described hereabove or by any of the well-known methods involving the condensation of bifunctional dicarboxylic acids and bifunctional diamines. Alternative methods are those described in Carothers Patents 2,130,523 and 2,130,948.

The temperature used for the copolymerization should be somewhat lower than that used for the homopolymerization, since the copolyamides are somewhat less stable to heat. Suitable temperatures range from about 250- 400 C. As in the case of homopolyamides, polymerization is generally effected in an inert atmosphere at atmospheric pressure, although it is somewhat advantageous to conduct the reaction under superatmospheric pressure to prevent the escape of volatile reactants, if such are used.

The choice of mole ratio of comonomers varies with the properties desired in the final product. If an aromatic comonomer is used with the monomer containing the benzothiazole unit, an excess of benzothiazole monomer is desirable, because the chief use of the product is in the production of molded objects of high stability to heat. The beneficial effects of aminobenzothiazole acid in raising melting points and increasing resistance to degradation are not apparent when less than about 5 mole percent of that component is present in the copolymer.

Similarly, a truly flexible, readily moldable and workable copolymer cannot be obtained unless aliphatic components comprise at least 30 mole percent of the polymer. As noted hereabove, the principal use for the copolyamides derived from an aliphatic comonomer is in the preparation of fibers. In this case an excess of the henzothiazole monomer would make the resulting product too stiff or brittle.

Our invention is further examples:

illustrated by the following Example 1 Acetic anhydride (45.0 g., 0.44 mole) was added during 20 minutes to a refluxing solution of dehydrothiop toluidine (99.0 g., 0.41 mole) in acetic acid (500 ml.). The mixture was stirred at reflux for an additional 1.5 hours and then cooled and poured in an equal volume of ice water. The tan solid was separated from the red liquid by filtration. The washed and dried solid (115.3 g). represented a quantitative yield of 2-(4-acetamidophenyl)-6-methylbenzothiazole, melting at 233-34.5 C.

Example II A solution of 2-(4'-acetamidophenyl)-6-methylb-enzothiazole (60.5 g., 0.22 mole) in pyridine (650 ml.) was added dropwise during one hour to a vigorously stirred solution of potassium permanganate (60.0 g., 0.38 mole) in water (200 ml.) and pyridine (100 ml.) at 60 C. After the complete addition, the mixture was heated to and stirred at 95 C. for one hour with the disappearance of the purple color. Additional potassium permanganate (60.0 g., 0.38 mole) was added and the reaction mixture was stirred at 95 C. for one hour with the disappearance of the purple color. Again potassium permanganate (40.0 g., 0.25 mole) was added and the mixture stirred and refluxed for three hours. The cooled brown mixture was filtered. Treating the brown filter cake with sodium bisulfite and concentrating the yellow pyridine filtrate gave yellow solids. The combined yellow solids were dissolved in 2500 ml. of 2% potassium hydroxide solution and filtered. Acidification of the yellow filtrate with hydrochloric acid gave 60.0 g. yield) of yellow solid, 2-(4'-acetamidophenyl)benzothiazole-6- carboxy-lic acid. No softening or 'melting could be detected below 330 C. on a standard melting point block. By dropping the powder onto a heated block at intervals of about 5 C., a rapid transition was noted at 320 C., the powder showing momentary softening then resolidifying. A purified sample gave the following elemental analysis:

Caled for C H N O S: Percent C, 61.62; 3.87; percent N, 8.97; 84.72. Found: Percent cent N, 8.92; percent S,

percent H, percent S, 10.26; percent total, C, 61.35; percent H, 3.95; per- 1'0.29; percent total, 84.51.

Example 111 A portion of 2-(4'-acetamidophenyl)benzothiazole-6- carboxylic acid (20.0 g.) was refluxed in a mixture of acetic acid (200 ml), 37% hydrochloric acid (300 ml.) and water (200 ml.) for five hours. The bright yellow suspension was cooled and filtered. The yellow solid was slurried with warm water, filtered and dried to yield 14.7 g. of yellow solid, infusible to over 360 C. The infrared spectrum was consistent with the structure proposed for 2-(4-aminophenyl)benzothiazole-6-carboxylic acid. The following elemental analysis was obtained:

Calcd for C H N O S: Percent C, 62.22; percent H, 3.73; percent N, 10.37; percent S, 11.86, percent total, 88.18. Found; Percent C, 62.01; percent H, 3.92; percent N, 10.46; percent S, 11.91, percent total, 88.33.

Example IV A sample (0.34. g.) of 2-(4'-aminophenyl)-6-'benzothiazolecarboxylic acid was placed in a tube, fitted with a nitrogen inlet and outlet, and heated in a silicone oil bath. The yellow acid underwent a slight darkening and sintering near 290 C. The darkening increased when the acid was heated to 360 C. during the next 0.5 hour. The cooled brown material was washed with hot dimethylformamide. Infrared analysis of the dimethylformamide-insoluble material established the presence of a secondary amide. No absorptions characteristic of an aryl carboxylic acid could be detected.

A sample of the preceding polymer (0.5 g.) was heated in a tube under a nitrogen atmosphere to- 505 C., and held at this temperature for one hour. Darkening and moderate shrinking occurred at about 460 C. At about 500 C., a trace of sublimate began to accumulate on the cooled part of the tube. The Dry Ice trap connected to the system collected a trace of liquid (0.0036 g.).

Example V 2-(4 aminophenyl)benzothiazole 6 carboxylic acid (0.013 mole) and a catalyst, the m-xylenediamine salt of isophthalic acid (0.1 g.), were mixed in a nitrogen atmosphere and heated in a silicone oil bath to 380 C. for nine hours. Condensate and a yellow sublimate began to appear at 260 C. and 320 C., respectively. After five hours at 260345 C., the condensate ceased to appear. Heating at 380 C. was continued for three hours. The cooled tan solid was extracted with first boiling pyri dine, then ethanol, leaving 3.0 g. (98% of theory) of insoluble tan solid. The infrared absorption spectrum was consistent with the proposed structure of poly-[2- (p-phenylene) -6-carboxamidobenzothiazole] exhibiting absorptions at 3.0 (NH), 6.08 1.

(amide II band), 12.1,u (p-substitution) and other absorptions characteristic of the desired polyamide. The elemental analysis of a sample gave the following results: Calcd for (C H N OS) C, 66.66%; H, 3.19%; N, 11.11%; S, 12.71%. Found: 66.63%; H, 3.28%; N, 10.90%; S, 12.48%. This remarkable agreement between caloulated and determined values shows that a high molecular weight polymer was formed.

The product thus obtained was evaluated by thermogravimetric analysis. Calculations of relative thermal stability, carried out by the method of C. D. Doyle (WADD TR 60-283, May 1960), gave an integral procedural decomposition temperature of 555 C. Reported values for other polymeric materials include 420 C. for nylon 66 and 405 C. fora nylon-phenolic resin.

Example VI In an attempt to obtain a polyamide having greater solubility, the condensation polymerization of 2-(4'-aminophenyl)benzot-hiazole-6-carboxylic acid was repeated at a lower temperature and over a longer period of time.

2 (4' aminophenyl)benzothiazole-6-carboxylic acid (3.5 g., 0.013 mole) and a catalyst, the m-Xylenediamine salt of isophthalic acid (0.08 g.), were thoroughly mixed and heated in an argon atmosphere via a silicone oil bath between 250315 C. for 25 hours. During the first 14 hours at 250-290 C., the weight loss was 0.17 g.

The infrared spectrum of a sample indicated that cssentially no condensation had occurred and the water collected was probably water of hydration. During the following five hours at 300-315 C., the weight loss was 0.26 g. The infrared spectrum indicated an appreciable amount of secondary amide and also the presence of some starting material. Additional heating at 300-315 C. during six hours resulted in a weight loss of 0.04 g. The resulting polyamide was washed with boiling pyridine followed by ethanol to give 3.0 g. (98% yield) of a tan solid. The infrared spectrum was consistent with the proposed structure of poly-[Z-(p-phenylene)-6-carboxamidobenzothiazole], exhibiting NH absorptions at 3.0 4, CONH and/or %N at 6.08 phenyl at 6.3 and 6.65 amide II band at 6.7544, para-substitution (two free hydrogen) at 12.05 and other absorptions characteristic of the desired polyamide.

In studying the solubility of the novel polyamide, a solution of each of the products of Examples V and VI was made in concentrated sulfuric acid. At a concentra tion of 0.5%, only a trace of floc remained undissolved in the acid at room temperature. Inherent viscosities found at 25 C. were 0.81 and 0.85. Efforts to dissolve the polyamide in hot dimethylsulfoxide gave a slight color to the solvent, but no detectable weight loss for the solid was noted. With formic acid (97%) (30 ml.), the polyamide (0.3 g.) gave no evidence of solution after one hour at 25 C. After raising the temperature to reflux and filtering hot, the residual solid weighed 0.28 g. The formic acid filtrate deposited a yellow fluffy solid after dilution with water.

Example VII 2 (4' acetamidophenyl) 6 benzothiazolecarboxylic acid (0.3750 g., 0.0012 mole) was heated under nitrogen atmosphere in a tube immersed in a molten salt bath. At 200 C., vapors evolved that were condensed in a Dry Ice cooled trap attached to the exit of the tube. The yellow acid gradually darkened as the temperature was increased from 300 to 435 C. for 45 minutes. The temperature was then increased to 535 C. during the next ten minutes. The material turned dark brown and appeared to decompose slightly at 520 C. After cooling, the dark brown, granular solid was washed with dimethylformamide. The dimethylformamide wash contained no starting material. Infrared analysis of the dark brown solid showed absorptions characteristic of a secondary amide, but no absorption characteristic of an aryl carboxylic acid could be detected. The liquid collected in the Dry Ice trap had the odor of acetic acid and was titrated with base. It was found that 0.7 mole of acetic acid was formed per mole of starting material. This would indicate that the average value for n in t 8 HO C tl t L .Nn. l.

is about 3.3, provided all of the evolved acid had been condensed by the trap.

Example VIII Example IX A mixture, 0.96 g. total, of equal weights of caprolactam and 2 (4' aminophenyl)-6-carboxybenzothiazole, was placed in a flask and While in a nitrogen atmosphere, subjected to a temperature increased via salt bat-h. The temperature was increased during one hour to 280. The yellow mixture turned a tan color and a liquid was collected in the Dry Ice trap. The tan mixture was then heated to 290 C. for one hour. During this period, more darkening occurred and the mixture became very viscous. The cooled brown solid was ground fine and washed with hot water to yield a yellow solid. The yellow solid was washed with dimet-hylformamide. The tan material, insoluble in dimethylformamide, weighed 0.4 g. Infrared analysis of a sample indicated it to be the desired polyamide and confirmed the presence of an aliphatic chain and aryl benzothiazole units. quantitative yield of the N-acetyl derivatives, M. 250-60" Example X C. This, in aqueous pyridine, oxidized by potassium permanganate, gave a 23% yield of the alkali-insoluble Small mixtures (2.0 g. total) were prepared and heated acetylamino-fi-carboxylic a ids. The oxidation cake at 250 C. for five hours under a it g n atmosphere, contained an even larger amount of the desired product. as follows: Sample 1. Caprolactam with 5% catalyst Example Sample 2. Caprolactam (80%) and 2-(4'-aminophenyl) O 5 g (001 m) of the acetylamino acid of Example gifts?th1azo1e-6-carboxyl1c acid with 5% cat- G g carefluny l f i with 0 11 m.) :i nglon r sat, i.e. t e sat o exarnet yene iamine an a lpic saglple f g i p g 10 acid. A drop of methanesulfonic acid was added, and lenzo laZo OXy 10 an 0) W1 0 ca the mixture heated with occasional shaking (in a nitrogen a atmosphere) to 200 C. over three hours, kept there three All three polymerization samples were fluid at about hours, then at 250 C. for six hours. A melt on a hot 200 C. Sample 1 was white, Sample 3 was light yellow 20 plate could be drawn into strings. A partial solution in and Sample 2 was deep yellow. At room temperature, dimethylsulfoxide, heated at 70 C. with aqueous formthe flexibility of small strips of the polymers was as folaldehyde and a drop of toluenesulfonic acid, lost most of lows: Sample 1-flexible, Sample 3moderately brittle its spectral amide absorptions and became completely inand Sample 2-very brittle. All three samples turned soluble. black at about 300 C. Infrared absorption spectra of We claim: 1 the three polymers showed the presence of polyamide and 1. A solid polymer consisting essentially of the followthe absence of measurable carboxylic acid absorption. ing recurring structural unit 0 0 H H o s S iii-l (rt/ n Ill \l LTCTR -N/-D lR-N |m o /o- /o- J t N l N J.-. Example XI wherein R is a member selected from the group consist- A mixture of equimolar amounts (0.015 mole) of ox mg of oxy'bls'phenylene arylene radicals having from bis(4-benzoic) acid (3.87 g.), 4,4-oxydianiline (3.00 g?) 6 16 carbon atoms i alkylene radlcills havmg from and 2 (4-aminophenyl)benzothiazole-6-carboxylic acid 242 carbon a p 15 Integer having a value of 1 (4.05 g.) was placed in a reactor equipped for nitrogen atx 18 an Integer having a f of 1 to m has a mosphere and heated to 350 C. during 10 hours. At mllumum value 9 1 and a maximum such that the 0 C condensates began to appear and at a 4 ratio of ml/n 18 no greater than 20, n has a value of 1, white sublimate appeared which was thought to be oxydiand q 15 an Integer havmg. value benzoic acid. A color change to green began to occur A copolym of clam 1 Wherem x 18 p 18 m is at 223 C. and to blue at 280 C. At this point, a small at least and R 15 hexanlethylene' amount of toluene was added to wash down the sublimate. A copolymeir of claim 1 wherein x p 18 m Is To prevent further sublimation, diphenyl ether was added at least *P R 1S 'p i 1 and the suspension refluxed (247 C.) for two hours. The A q polymer conlstlng essentlauy of the to 10W- solvent was removed and the blue solid heated to 350 C. mg recurring Structural umt during three hours. The polymeric blue solid was boiled O s S in several portions of ethanol and dried to yield 7.75 g. n 1 (77% of theory). The infrared spectrum exhibited absorptions at 3.04 bonded N-H; 6.0m, -CONH-; L L J J 655 amide II band; 809 aryl ether; 120p, para-sub- N N Y stitution. Other weak absorptions characteristic of the wherein x is an integer having a value of 1 to 5 and y is benzothiazole unit were also present. The infrared specan integer having a value of at least 2. trum was consistent with the proposed structureof the ex- 5. Method of making a solid polymer consisting espected polyamide. A 1.0 g. sample was stirred in 50 ml. sentially of the following recurring structural unit of concentrated sulfuric forming a clear dark green solus S tion. Dilution with water gave a green solid which was r 1 l L washed wih dilute sodium hydroxide solution followed G by water to give 0.95 g. of blue solid having an infrared spectrum identical to the starting blue polyamide. A N y sample submitted for elemental analysis gave the following results: wltrereinhx is an rntelger hfavirig a vglue of 1 to 5 and y is an 1n eger avm ava ue o a cast com risin reactin at Calcd for 4o 2s 4 5 )n Percent C, 71-20; Percent H, a temperaturi of l80450 C. a compibund of the f or- 3.88; percent N, 8.31; percent S, 4.75; percent total, mula; 88.14. Found: Percent C, 60.67; percent H, 3.73; percent N, 7.11; S S

percent S, 7.03; percent total, 78.54. mo 0 The differences can be attributed to the sublimation loss 0 L of the oxy-bis-(4-benzoic) acid during the initial con- 7 N N Jx-l densatlon' Example XII wherein x has the value given aforesaid, R is a member t selected from the group consisting of hydroxy, hydrogen, Crude commercial primulme base was freed of toluidine 75 lower alkoxy and phenoxy and R is a member selected and sulfur, leaving as residue a mixture of predominantly 10 2-(p-aminophenyl) -6-methyl-2,6'-bibenzothiazole (x: 1 plus some of the higher homologs (x=2-5). Refluxing a solution of 10 g. of this in 200 ml. acetic acid and 4 g. acetic anhydride three hours, then pouring on ice, gave a from the group consisting of hydrogen and alkanoyl.

6. Method according to claim 5 wherein the reaction is wherein R, R and R have the values given aforesaid conducted in an inert atmosphere. and

7. Method of making a solid copolymer consisting es- (b) an equimolar mixture of the compounds sentially of the following recurring structural unit (1) R HNRNHR wherein R is a member selected from the group consisting N wherein R, R and R have the values given aforesaid, but of arylene radicals having from 6-16 carbon atoms and may represent a different member of the same group in alkylene radicals having from 2-12 carbon atoms, p is an each of the compounds (1) and (2), the value of p being integer having a value of 1 to 2, x is an integer having a 1 when member (a) is selected and 2 where member (b) value of 1 to 5, 172 has a minimum value of 2 and a maxiis selected, and the mole ratio of the reactants being govmum value such that the ratio of m-l/n is no greater erned by the ratio of m-l/n defined aforesaid. than 20, n has a value of l, and q is an integer having a 8. Method according to claim 7 wherein the reaction value of at least 2, comprising reacting at a temperature is conducted in an inert atmosphere.

of 180450 C. a compound of the formula: 20

. s s References Cited by the Examiner {I 1 UNITED STATES PATENTS R100 0 C 2,972,603 2/1961 Cislak 260-79 L J,, 3,047,543 7/1962 Morton etal 25 wherein x has the value given aforesaid, R is a member 3110701 12/1963 Wear 260 /8 selected from the group consisting of hydrogen, hydroxy, lower alkoxy and phenoxy and R is a member selected WILLIAM SHORT, 'y Examinerfrom the group consisting of hydrogen and lower alkanoyl, H ANDERSON, Assistant Examinel. with 'a member selected from the group consisting of 0 

1. A SOLID POLYMER CONSISTING ESSENTIALLY OF THE FOLLOWING RECURRING STRUCTURAL UNIT 